Sequential reduction of the silicon single-electron transistor structure to atomic scale.

Here we present an original CMOS compatible fabrication method of a single-electron transistor structure with extremely small islands, formed by solitary phosphorus dopants in the silicon nanobridge. Its key feature is the controllable size reduction of the nanobridge in sequential cycles of low energy isotropic reactive ion etching that results in a decreased number of active charge centers (dopants) in the nanobridge from hundreds to a single one. Electron transport through the individual phosphorous dopants in the silicon lattice was studied. The final transistor structure demonstrates a Coulomb blockade voltage of ∼30 mV and nanobridge size estimated as [Formula: see text]. Analysis of current stability diagrams shows that electron transport in samples after the final etching stage had a single-electron nature and was carried through three phosphorus atoms. The fabrication method of the demonstrated structure allows it to be modified further by various impurities in additional etching and implantation cycles.

STM study of morphology and electron transport features in cytochrome c and nanocluster molecule monolayers.

The morphology and electron tunneling through single cytochrome c and nanocluster Pt(5)(CO)(7)[P(C(6)H(5))](4) molecules organized as monolayer Langmuir-Blodgett (LB) films on graphite substrate have been studied experimentally using scanning tunneling microscopy (STM) and spectroscopy techniques with sub-nanometer spatial resolution in a double barrier tunnel junction configuration STM tip-monomolecular film-conducting substrate at ambient conditions. STM images of the films revealed globular structures with characteristic diameters (approximately 3.5 nm for the protein molecule and approximately 1.2 nm for the nanocluster). The spectroscopic study by recording the tunneling current-bias voltage (I-V) curves revealed tunneling I-V characteristics with features as steps of different width and heights that are dependent on the STM tip position over the molecule in the monolayer, giving evidence for sequential discrete electron-tunneling effects with the combination of the single electron Coulomb-charging energy and the electronic energy level separation (molecular spectrum) in such immobilized metalloprotein and nanocluster structures that can be of interest for the development of bioelectronic and hybrid functional nanosystems.

Interaction of copper ions with stearic acid Langmuir monolayers and formation of cluster structures in monolayers and Langmuir-Blodgett films.

The interaction of copper ions with a stearic acid Langmuir monolayer resulting in an extremely high level of copper binding to the monolayer in amounts much larger than the number of stearic acid molecules in the monolayer was studied. The shape of the pressure-area isotherm changed drastically upon pH changes from 4 to 6 in the presence of copper ions in the aqueous phase (at concentrations of 10(-5) to 10(-3)(M) or upon addition of copper ions to the aqueous phase under different monolayer compressions. The copper ion concentration changes in the bulk phase, caused by binding to the monolayer, were studied by EPR at the equilibrium after intensive mixing of the bulk phase and were found to depend on pH of the aqueous phase and the extent of monolayer compression. The highest level of binding (up to 100 copper ions per stearic acid molecule, pH 5.6, initial copper concentration 5.10(-4) M) was observed at a surface pressure of about 20 mN/m; further compression of the monolayer and the respective increase in surface pressure caused the reverse growth of aqueous phase copper ion concentration. At the collapse and destruction of the monolayer, the copper ion concentration in the bulk phase was similar to that in the absence of the monolayer. The EPR spectra and SAXS diffractograms of copper-containing stearic acid monolayers confirmed the high copper content in LB films obtained. An STM study of pure stearic acid and the copper-containing monolayer LB films, transferred to graphite wafers from the water subphase surface (pH 5.4) at various copper concentrations, discovered nanosized (about 5 nM) cluster formations on the monolayer surface. The data obtained indicate that the interaction of a charged Langmuir monolayer with copper ions and formation of copper-containing nanostructures depends on monolayer compression and is determined by the arrangement, order, mobility of the monolayer stearic acid molecules and by electrostatics at the interface.